Method for image formation and intermediate transfer recording medium

ABSTRACT

The present invention provides a method for image formation, that can yield thermally transferred images which are excellent in various fastness properties even under severe service conditions, and an intermediate transfer recording medium for use in the method for image formation. The method for image formation comprises the steps of: providing an intermediate transfer recording medium comprising a substrate film and a transfer portion provided separably on the substrate film; forming an image on the intermediate transfer recording medium in its transfer portion; transferring the transfer portion onto an object; and, thereafter, again transferring the intermediate transfer recording medium in its next transfer portion once or more onto the object with the image formed thereon. In this case, in the intermediate transfer recording medium, a hologram image is set every at least second image plane, and an image can be formed on the transfer portion having the hologram image. This can offer an advantage that the transfer portion, with a thermally transferable image formed thereon, can be transferred onto an object followed by the superimposition of a transfer portion, to be served as the outermost surface in the final form onto the transferred portion once or more to provide a strong film for protecting the thermally transferred image. Thus, the problems of the prior art could have been solved.

TECHNICAL FIELD

The present invention relates to a method for image formation which canyield a thermally transferred image possessing excellent variousfastness properties even under severe service conditions, and anintermediate transfer recording medium for use in the method for imageformation.

BACKGROUND ART

Thermal transfer has become extensively used as a simple printingmethod. The thermal transfer is a method which comprises the steps of:putting a thermal transfer sheet, comprising a colorant layer providedon one side of a substrate sheet, on top of a thermal transferimage-receiving sheet optionally provided with an image-receptive layer;an image-wise heating the backside of the thermal transfer sheet byheating means such as a thermal head to selectively transfer thecolorant contained in the colorant layer to form an image on the thermaltransfer image-receiving sheet.

Thermal transfer methods are classified into thermal ink transfer (hotmelt-type thermal transfer) and sublimation dye thermal transfer(sublimation-type thermal transfer). The thermal ink transfer is amethod for image formation wherein a thermal transfer sheet comprising asubstrate sheet, such as a PET film, bearing thereon a hot-melt inklayer, formed of a dispersion of a colorant, such as a pigment, in abinder, such as a hot-melt wax or resin, is provided and energyaccording to image information is applied to heating means such as athermal head to transfer the colorant together with the binder onto athermal transfer image-receiving sheet such as paper or plastic sheets.Images produced by the thermal ink transfer have high density andpossesses high sharpness and are suitable for recording binary images ofcharacters or the like.

On the other hand, the sublimation dye thermal transfer is a method forimage formation which comprises the steps of: providing a thermaltransfer sheet comprising a substrate sheet, such as a PET film, bearingthereon a dye layer formed of a dye, which is mainly thermallytransferred by sublimation, dissolved or dispersed in a resin binder;and applying energy according to image information to heating means suchas a thermal head to transfer only the dye onto a thermal transferimage-receiving sheet comprising a substrate sheet, such as paper or aplastic, optionally provided with a dye-receptive layer. The sublimationdye thermal transfer can regulate the amount of the dye transferredaccording to the quantity of energy applied and thus can form gradationimages of which the image density has been regulated dot by dot of thethermal head. Further, since the colorant used is a dye, the formedimage is transparent, and the reproduction of intermediate colorsproduced by superimposing different color dyes on top of each other orone another is excellent. Accordingly, high-quality photograph-like fullcolor images can be formed with excellent reproduction of intermediatecolors by transferring different color dyes, such as yellow, magenta,cyan, and black, onto a thermal transfer image-receiving sheet, so as tosuperimpose the color dyes on top of each other or one another, from athermal transfer sheet of the different colors.

Thermal transfer image-receiving sheets on which images will be formedby these thermal transfer methods have various practical applications.Representative examples of applications include proof sheets, andrecording sheets for output images, output plans or designs drawn byCAD/CAM or the like, or images output from a variety of medicalanalyzers or measuring instruments such as CT scanners and endoscopiccameras. They can also be used as the alternative of instantphotographs, and as paper for producing identity certifications, IDcards, credit cards, and other cards on which facial photographs or thelike are printed, or for producing synthetic or memorial photographswhich are taken at amusement facilities such as recreation parks, gamecenters, museums, aquariums and the like. The diversification ofapplications has led to an increasing demand for the thermal transfer ofan image on any desired object. A method has been proposed, as onemethod for meeting this demand, wherein a colorant such as a dye or apigment is transferred, from a thermal transfer sheet comprising a dyelayer or a hot-melt ink layer, onto a receptive layer in an intermediatetransfer recording medium comprising the receptive layer separablyprovided on a substrate to form an image on the receptive layer and,thereafter, the intermediate transfer recording medium is heated totransfer the receptive layer, with the image formed thereon, onto anobject (Japanese Patent Laid-Open No. 238791/1987 or the like).

Since the use of the intermediate transfer recording medium permits thereceptive layer to be transferred onto an object, this method ispreferably used, for example, for objects, onto which a colorant is lesslikely to be transferred making it impossible to form high-qualityimages directly on them, and objects which are likely to be fused to thecolorant layer at the time of thermal transfer. Further, a method mayalso be used wherein necessary matters such as signatures or the likeare previously written or printed on an object and, thereafter, atransfer portion with an image of characters, a photograph or the likeformed thereon is transferred from the intermediate transfer recordingmedium to prepare a print. Therefore, the intermediate transferrecording medium is preferably used in the preparation of passports orother identity certifications, credit cards/ID cards, or other prints.

Securities, that is, high reliability/safety, which means a high levelof difficulty of forgery or alteration, are required of theabove-described prints such as passports or credit cards. To make itdifficult to perform forgery, alteration or the like by copying, variousdevices have hitherto been made.

The present applicant has already filed applications regarding anintermediate transfer recording medium having in its transfer portion ahologram pattern, micro-characters, etc., and a print produced bytransferring the transfer portion onto an object, for preventing theforgery and alteration of passports, credit cards, or other prints(Japanese Patent Laid-Open Nos. 254844/1999 and 15939/2000). Accordingto these techniques, the transfer of the hologram pattern ormicro-characters, provided in the transfer portion, together with theimage onto an object makes it difficult to forge and alter images, suchas characters or a facial photograph, formed in the print and thus canrealize high reliability and safety.

DISCLOSURE OF THE INVENTION

The formation of an image on an object using the conventionalintermediate transfer recording medium, however, poses a problem thatthe image face in the transfer portion of the intermediate transferrecording medium comes into contact with the object and thus, although afilm is formed on the outermost surface of the image on the object, theimage, when exposed to service conditions which are severe in terms ofvarious fastness properties, particularly chemical resistance,lightfastness and weathering resistance, is damaged.

Accordingly, it is an object of the present invention to solve the aboveproblem of the prior art and to provide a method for image formation,which can yield a thermally transferred image having excellent variousfastness properties even under severe service conditions, and anintermediate transfer recording medium for use in the method for imageformation.

The above object of the present invention can be attained by a methodfor image formation, comprising the steps of: providing an intermediatetransfer recording medium comprising at least a substrate film and atransfer portion provided separably on the substrate film; forming animage on the intermediate transfer recording medium in its transferportion; transferring the transfer portion onto an object; and,thereafter, again transferring the intermediate transfer recordingmedium in its next transfer portion once or more onto the object withthe image formed thereon.

In the intermediate transfer recording medium, preferably, a hologramimage is set every at least second image plane and an image is formed onthe transfer portion having the hologram image.

Another method for image formation according to the present inventioncomprises the steps of: providing an intermediate transfer recordingmedium with a hologram, wherein a transfer portion is provided which hasat least two different hologram images alternately provided in the imageplane portions as counted on the assumption that one image is set in oneimage plane; forming an image on the transfer portion in its regionhaving one type of hologram image; transferring the transfer portiononto an object; and, thereafter, again transferring the intermediatetransfer recording medium, with a hologram, in its next transfer portiononce or more onto the object with the image formed thereon.

According to the present invention, there is provided an intermediatetransfer recording medium comprising: at least a substrate film; and atransfer portion provided separably on the substrate film, wherein ahologram image is set every at least second image plane in the transferportion of the intermediate transfer recording medium.

Another intermediate transfer recording medium according to the presentinvention comprises: at least a substrate film; and a transfer portionprovided separably on the substrate film, wherein at least two differenthologram images are provided alternately in the transfer portion ascounted on the assumption that one image is set in one image plane.

In the present invention, an intermediate transfer recording mediumcomprising at least a substrate film and a transfer portion providedseparably on the substrate film is provided, and an image is formed onthe intermediate transfer recording medium in its transfer portion. Thetransfer portion is transferred onto an object, and, thereafter, theintermediate transfer recording medium in its next transfer portion isagain transferred once or more onto the object with the image formedthereon. In this case, preferably, a hologram image is set every atleast second image plane and an image is formed on the transfer portionhaving the hologram image.

In again transferring the intermediate transfer recording medium in itsnext transfer portion once or more on the object with the thermallytransferred image formed thereon, preferably, the intermediate transferrecording medium in its next transfer portion is specificallytransferred approximately once to three times. When the number of timesof transfer is excessively large, unfavorable phenomena occur includingthat the level of irregularities on the surface of the print is large,the adhesion of the transfer portion to the object is lowered, and thethermally transferred image is blurred due to a lowering in transparencyof the transferred portion located on the thermally transferred image.

In another method for image formation according to the presentinvention, an intermediate transfer recording medium with a hologram,wherein a transfer portion is provided which has at least two differenthologram images alternately provided in the image plane portions ascounted on the assumption that one image is set in one image plane, isprovided, and an image is formed on the transfer portion in its regionhaving one type of hologram image. The transfer portion is transferredonto an object, and, thereafter, the intermediate transfer recordingmedium with a hologram, in its next transfer portion is againtransferred once or more onto the object with the image formed thereon.

In again transferring the intermediate transfer recording medium with ahologram, in its next transfer portion once or more onto the object withthe thermally transferred image formed thereon, preferably, theintermediate transfer recording medium with a hologram, in its nexttransfer portion is specifically transferred approximately once to threetimes. The reason for this is as described above.

Thus, the transferred portion with the thermally transferred imageformed thereon is provided on the object, and the transferred portion asthe outermost surface in the final form of the print is superimposedonce or more on the transferred portion with the thermally transferredimage formed thereon. By virtue of this, a strong film for protectingthe thermally transferred image can be provided, and, even when theprint is exposed to severe service conditions, the thermally transferredimage has excellent various fastness properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing one embodiment of theintermediate transfer recording medium according to the presentinvention;

FIG. 2 is a plan view showing another embodiment of the intermediatetransfer recording medium according to the present invention;

FIG. 3 is a partially enlarged cross-sectional view showing a furtherembodiment of the intermediate transfer recording medium according tothe present invention;

FIG. 4 is a cross-sectional view showing one embodiment of a final printproduced by the present invention;

FIG. 5 is a cross-sectional view showing another embodiment of a finalprint produced by the present invention; and

FIG. 6 is a cross-sectional view showing a further embodiment of a finalprint produced by the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a cross-sectional view showing one embodiment of theintermediate transfer recording medium according to the presentinvention. An intermediate transfer recording medium 1A comprises asubstrate film 2 and a transfer portion 8 separably provided on thesubstrate film 2. A hologram image 10 is provided in the transferportion 8 every second image plane. The transfer portion 8 comprises ahologram layer 4 and a receptive layer 3. The hologram image 10 isformed in the hologram layer 4 every second image plane 13. After theimage plane portion 13A with a thermally transferred image formedthereon (in which a thermally transferred image is located on thereceptive layer on the hologram image) is transferred onto an object,the image plane portion free from the hologram image 10, that is, aimage plane portion 13B, is put on top of the hologram image 10 and istransferred onto the object so as to constitute the outermost surface inthe final form. Thus, the transfer portion 8 in its image plane portion13B free from the hologram image 10, when transferred onto the object,functions to protect the thermally transferred image in the print.

FIG. 2 is a cross-sectional view showing another embodiment of theintermediate transfer recording medium. An intermediate transferrecording medium 1B comprises a substrate film 2 and a transfer portion8 separably provided on the substrate film 2. Different hologram images,i.e., a hologram image 10A and a hologram image 10B, are alternately andrepeatedly formed in a face serial manner in a hologram layer 4 in thedirection of flow of the intermediate transfer recording medium 1B ascounted on the assumption that one image is set in one image plane. Inthe transfer portion 8, a hologram layer 4 and a receptive layer 3, onwhich an image is to be formed, are provided in that order from thesubstrate film 2 side. For example, when an image has been thermallytransferred on the receptive layer 3 in its portion provided on thehologram image 10A, after the transfer of the image plane portion 13Awith the hologram image 10A onto an object, the image plane portion 13Bwith the hologram image 10B free from the thermally transferred imagecan be transferred so as to be superimposed on the hologram image 10A.

FIG. 3 is a partially enlarged cross-sectional view showing a furtherembodiment of the intermediate transfer recording medium according tothe present invention. An intermediate transfer recording medium 1Ccomprises: a substrate film 2; and, stacked on the substrate film 2 inthe following order, a peel layer 5, a hologram layer 4, a transparentvapor deposited layer 6, an anchor layer 7, and a receptive layer 3. Ahologram image 10 (pattern) is provided in the hologram layer 4.Micro-characters and a color figure pattern may also be formed in atransfer portion 8 comprising the peel layer 5, the hologram layer 4,the transparent vapor deposited layer 6, the anchor layer 7, and thereceptive layer 3. In this intermediate transfer recording medium 1C,the transfer portion 8 after the formation of a thermally transferredimage 9 is transferred onto an object, and, another transfer portion(not shown) adjacent to the portion, in which the image has beenthermally transferred, is transferred onto the thermally transferredimage 9 to prepare a print.

In the transfer portion 8 shown in FIG. 3, the layers other than thereceptive layer 3 and the hologram layer 4, for example, the peel layer5, the transparent vapor deposited layer 6, and the anchor layer 7, arenot always indispensable and may be properly selected and provided, forexample, according to the material of the object, the applications ofthe print, and the form of use, that is, are not particularly limited.Therefore, instead of or in addition to these layers, a layer having aspecific function such as an ultraviolet absorbing layer may be properlyselected and provided. The transparent vapor deposited layer 6 and theanchor layer 7 are in many cases provided together with the hologramlayer 4.

Elements constituting the intermediate transfer recording medium will bedescribed.

Hologram Image

The size and shape of the hologram image (pattern) 10 may vary dependingupon the form of prints required and thus are not particularly limited.The hologram image is formed by a conventional method, for example, by amethod wherein an original plate provided with a concave-convex patternof interference fringes of a hologram is provided and fine concaves andconvexes are formed by embossing or the like.

The hologram layer 4 is generally a resin layer, and this layer per semay have a single-layer structure or a multilayer structure. In thepresent invention, the hologram layer, when transferred onto the object,has the function of protecting the thermally transferred image to impartvarious fastness properties to the image.

The hologram layer may be formed of a planar hologram or a volumehologram. In the case of the planar hologram, among others, a reliefhologram is preferred from the viewpoints of mass productivity and cost.Other holograms usable herein include: holograms reproducible by laser,such as Fresnel holograms, Fraunhofer holograms, lensless Fouriertransformation holograms, and image holograms; holograms reproducible bywhite light, such as rainbow holograms; and holograms utilizing theseprinciples, for example, color holograms, computer holograms, hologramdisplays, Multiflex holograms, holographic stereograms, and holographicdiffraction gratings.

Photosensitive materials for the hologram layer for recording interferefringes include silver salts, gelatin bichromate, thermoplastics, diazophotosensitive material photoresists, ferroelectrics, photochromicsmaterials, and chalcogen glasses. Materials for the hologram layersusable herein include: thermoplastic resins, such as polyvinyl chloride,acrylic resins (for example, polymethyl methacrylate), polystyrene, andpolycarbonates; cured products of thermosetting resins, such asunsaturated polyesters, melamine, epoxy, polyester (meth)acrylate,urethane (meth)acrylate, epoxy (meth)acrylate, polyether (meth)acrylate,polyol (meth)acrylate, melamine (meth)acrylate, and triazine acrylate;cured products of ultraviolet-curable resins, such as compositionscomprising a sensitizer added to a proper mixture of an unsaturatedethylene monomer with an unsaturated ethylene oligomer; mixtures of theabove thermoplastic resins with the above thermosetting resins; andthermoformable materials having a radically polymerizable unsaturatedgroup. In particular, thermosetting resins and ultraviolet-curableresins are preferred as the resin for the hologram layer from theviewpoint of excellent fastness properties, such as excellent chemicalresistance, lightfastness, and weathering resistance.

Substrate Film

The substrate film 2 is not particularly limited, and the same substratefilm as used in the conventional intermediate transfer recording mediumas such may be used as the substrate film 2. Specific preferred examplesof the substrate film 2 include: thin paper, such as glassine paper,capacitor paper, or paraffin-waxed paper; and stretched or unstretchedfilms of plastics, for example, highly heat resistant polyesters, suchas polyethylene terephthalate, polyethylene naphthalate, polybutyleneterephthalate, polyphenylene sulfide, polyether ketone, or polyethersulfone, and other plastics, such as polypropylene, polycarbonate,cellulose acetate, polyethylene derivative, polyvinyl chloride,polyvinylidene chloride, polystyrene, polyamide, polyimide,polymethylpentene, or ionomer. Further, composite films comprising alaminate of two or more materials selected from the above materials mayalso be used. The thickness of the substrate film 2 may be properlyselected according to the material so as to provide proper strength,heat resistance and other properties. In general, however, the thicknessof the substrate film 2 is preferably about 1 to 100 μm.

If necessary, a backside layer may be provided by a conventional methodon the substrate film in its side remote from the transfer portion. Thebackside layer may be provided for preventing the substrate film frombeing fused to a heating device, such as a thermal head, at the time ofthe transfer of the transfer portion onto the object using theintermediate transfer recording medium and for improving the slidabilityand may be formed of the same resin as used in the prior art.

Receptive Layer

The receptive layer 5 is provided as a part of the transfer portionconstituting the intermediate transfer recording medium so as to locateon the outermost surface remote from the substrate film. An image isformed by thermal transfer on the receptive layer from a thermaltransfer sheet having a colorant layer. The intermediate transferrecording medium in its transfer portion with the image formed thereonis transferred onto an object, and, thus, a print is formed.

For this reason, a conventional resin material, which is receptive to athermally transferable colorant such as a sublimable dye or a hot-meltink, may be used as the material for the receptive layer. Examples ofmaterials usable herein include: polyolefin resins such aspolypropylene; halogenated resins such as polyvinyl chloride orpolyvinylidene chloride; vinyl resins such as polyvinyl acetate, vinylchloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, orpolyacrylic ester; polyester resins such as polyethylene terephthalateor polybutylene terephthalate; polystyrene resin; polyamide resin;resins of copolymers of olefins, such as ethylene or propylene, withother vinyl polymers; ionomers; cellulosic resins such as cellulosediastase; and polycarbonates. Vinyl chloride resins, acryl-styreneresins, or polyester resins are particularly preferred.

When the receptive layer is transferred through an adhesive layer ontoan object, the receptive layer per se is not always required to beadhesive. On the other hand, when the receptive layer is transferredonto the object without through the adhesive layer, the formation of thereceptive layer using a resin material having adhesive properties, suchas vinyl chloride-vinyl acetate copolymer, is preferred.

The receptive layer may be formed by dissolving or dispersing a singleor plurality of materials, selected from the above materials, optionallymixed with various additives or the like, in a suitable solvent such aswater or an organic solvent to prepare a coating liquid for a receptivelayer, coating the coating liquid by means such as gravure printing,image plane printing, or reverse coating using a gravure plate, anddrying the coating. The thickness of the receptive layer is about 1 to10 μm on a dry basis.

Peel Layer

The peel layer 5 is generally formed of, for example, a mixture of aresin having an acryl skeleton, a vinyl chloride-vinyl acetatecopolymer, or cellulose acetate with a heat-curable acrylic resin, amelamine resin, a nitrocellulose resin, and polyethylene wax. The peellayer composed mainly of the resin having an acryl skeleton isparticularly preferred. Further, a polyester resin and the like arepreferably used for regulating the adhesion between the peel layer andthe substrate film.

The peel layer may be formed, for example, by dissolving or dispersing aresin having an acryl skeleton and a polyester resin in a suitablesolvent to prepare a coating liquid for a peel layer, coating thecoating liquid onto a substrate film by means such as gravure printing,image plane printing, or reverse printing using a gravure plate, anddrying the coating. The thickness of the peel layer is generally 0.1 to10 μm on a dry basis.

Further, even in the case of a transfer portion not provided with a peellayer, suitable adhesion between the hologram layer and the substratefilm can be imparted by rendering the hologram layer separable.Furthermore, the same function as in the peel layer can be imparted tothe substrate film by imparting separability to the substrate film perse.

Instead of the peel layer, a release layer (not shown) may be providedon the substrate film. The release layer is generally formed of a binderresin and a releasable material. Binder resins include: thermoplasticresins, for example, acrylic resins such as polymethyl methacrylate,polyethyl methacrylate, and polybutyl acrylate, vinyl resins such aspolyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinylalcohol, and polyvinyl butyral, cellulose derivatives such asethylcellulose, nitrocellulose, and cellulose acetate; and thermosettingresins, for example, unsaturated polyester resins, polyester resins,polyurethane resins, and amino-alkyd resins. Releasable materials usableherein include waxes, silicone waxes, silicone resins, melamine resins,fluororesins, fine powders of talc or silica, and lubricating agentssuch as surfactants and metallic soaps.

The release layer may be formed by dissolving or dispersing the aboveresin in a suitable solvent to prepare a coating liquid for a releaselayer, coating the coating liquid onto a substrate film by means such asgravure printing, image plane printing, or reverse coating using agravure plate, and drying the coating. The thickness of the releaselayer is generally 0.1 to 10 μm on a dry basis.

Transparent Vapor Deposited Layer

The transparent vapor deposited layer 6 is generally provided on thereceptive layer side so as to contact with the hologram layer. Thistransparent vapor deposited layer has a refractive index different fromother layers and thus functions to allow the hologram pattern in theprint to be seen as if the pattern is in a floated state. Thetransparent vapor deposited layer may be formed of any conventionalmaterial without particular limitation, for example, a metal oxide ormetal sulfide such as ZnS, TiO₂, SiO₂, or Cr₂O₃. The transparent vapordeposited layer may be formed by a conventional method such as vacuumdeposition or sputtering.

Anchor Layer

For example, in FIG. 3, the anchor layer 7 is provided so as to adherethe hologram layer 4 having on its surface the transparent vapordeposited layer 6 to the receptive layer 3. The anchor layer may beformed of a conventional material without particular limitation. Theformation method may also be the same as used in the prior art.

Ultraviolet Absorbing Layer

If necessary, an ultraviolet absorbing layer may be provided as a partof the transfer portion at a suitable position between the receptivelayer and the substrate film. This ultraviolet absorbing layer coversthe transferred receptive layer to prevent the image in the print frombeing deteriorated by ultraviolet light contained in natural light. Theultraviolet absorbing layer may be formed of a conventional materialwithout any particular limitation. The formation method may also be thesame as used in the prior art.

Object

Next, an object 11 will be described. The intermediate transferrecording medium in its transfer portion with a thermally transferredimage formed thereon is transferred onto the object, and, again, theintermediate transfer recording medium in its next transfer portion isfurther transferred once or more onto the image on the object to preparea print provided with a thermally transferred image possessing excellentvarious fastness properties. The object to which the intermediatetransfer recording medium according to the present invention is appliedis not particularly limited, and examples thereof include natural fiberpaper, coated paper, tracing paper, plastic films which are not deformedupon exposure to heat at the time of transfer, glasses, metals,ceramics, wood, and cloths.

Regarding the form and applications of the object, there is nolimitation on the type, and examples thereof include: gold notes, suchas stock certificates, securities, deeds, passbooks, railway tickets,streetcar tickets, stamps, postage stamps, appreciation tickets,admission tickets, and other tickets; cards, such as bank cards, creditcards, prepaid cards, membership cards, greeting cards, postcards,business cards, driver's licenses, IC cards, and optical cards; cases,such as cartons and containers; bags; forms control; envelops; tags; OHPsheets; slide films; bookmarks; calendars; posters; pamphlets; menus;passports; POP goods; coasters; displays; name plates; keyboards;cosmetics; accessories such as wristwatches and lighters; stationeriessuch as report pads; building materials; panels; emblems; keys; cloths;clothes; footwears; equipment or devices such as radios, televisions,electronic calculators, and OA equipment; various sample or patternbooks; albums; and outputs of computer graphics and outputs of medicalimages.

Method For Image Formation

Next, the method for image formation according to the present invention,wherein an image is thermally transferred onto any object using theabove intermediate transfer recording medium, will be described.

At the outset, the above intermediate transfer recording medium and athermal transfer sheet comprising a colorant layer provided on asubstrate are provided. The intermediate transfer recording medium isput on top of the thermal transfer sheet so that the transfer portion inthe intermediate transfer recording medium comes into contact with thecolorant layer in the thermal transfer sheet. The assembly is pressedbetween a heating device, such as a thermal head, and a platen roll. Aheating portion in the heating device is selectively heated in responseto image information to transfer the colorant of the colorant layer inthe thermal transfer sheet onto the receptive layer in the intermediatetransfer recording medium, thereby recording an image.

The thermal transfer sheet may be any conventional one. The colorantlayer provided in the thermal transfer sheet is formed of a hot-melt inkor an ink containing a sublimable dye. The colorant layer is formed of ahot-melt ink or a sublimable dye ink which is properly selecteddepending upon the contemplated print. The colorant layer formed of asublimable dye used in the formation of a print with good gradation maybe formed by properly providing conventional sublimable dyes such asyellow, magenta, cyan, and black according to need in a face serialmanner. On the other hand, in the case of monochromatic binary images ofcharacters, numerals and the like, a thermal transfer sheet comprising acolorant layer formed of a hot-melt ink possessing excellent density andsharpness may be used alone. Alternatively, a thermal transfer sheetcomprising a colorant layer formed of the sublimable dye and a hot-meltink layer, which have been provided in a face serial manner, may beused.

As shown in FIG. 4, an image 9 corresponding to one image plane as theprint is thermally transferred onto the intermediate transfer recordingmedium 1 in its transfer portion 8A (receptive layer 3). Next, thetransfer portion 8A with the thermally transferred image 9 formedthereon is pressed against the object 11 so that the image face of thetransfer portion 8A comes into contact with the object 11, and thetransfer portion 8A is transferred onto the object 11 by heating meanssuch as a thermal head, a hot stamp, or a hot roll. In the means forheating the transfer portion 8A, for partial transfer, the use of athermal head or a hot stamp is preferred, while, for transfer onto thewhole surface of the object, a hot roll method is preferred.

Further, the intermediate transfer recording medium 1 in its transferportion 8B adjacent to the transfer portion 8A, with the image 9thermally transferred thereon, which has been transferred onto theobject 11, or an intermediate transfer recording medium, which isdifferent from the intermediate transfer recording medium 1 with theimage 9 thermally transferred thereon, in its transfer portion 8B istransferred so as to cover the thermally transferred image 9 on theobject 11. Thus, a final print 12 is prepared.

A print 12 shown in FIG. 4 has a construction comprising a firsttransferred portion 8A and a next transferred portion 8B. Both thetransferred portions 8A and 8B have been transferred from anintermediate transfer recording medium comprising a receptive layer 3provided on a film substrate through an intermediate layer 14 which issatisfactory in fastness properties such as chemical resistance,lightfastness, and weathering resistance. Examples of resins usable forforming the intermediate layer include: thermoplastic resins, such aspolyester resin, polystyrene resin, acrylic resin, polyurethane resin,acrylated urethane resin, epoxy resin, phenoxy resin, products ofmodification of these resins with silicone, and mixtures of theseresins; ionizing radiation-curable resins; and ultraviolet screeningresins. If necessary, ultraviolet absorbers, organic fillers and/orinorganic fillers may also be properly added. FIG. 5 is across-sectional view showing one embodiment of the final print producedaccording to the present invention. The print shown in FIG. 5 has thesame construction as the print shown in FIG. 4, except that a hologramlayer 4 has been provided instead of the intermediate layer. In theintermediate transfer recording medium used, the transfer portionprovided on the substrate film comprises a hologram layer 4 and areceptive layer 3 provided in that order on a substrate film. A hologramimage 10 is provided in the hologram layer 4 every at least second imageplane, and an image is thermally transferred onto the transfer portion8A with the hologram image 10 formed thereon. Next, the transfer portion8A with the image formed thereon is transferred onto an object 11.Thereafter, the transfer portion 8B comprising the hologram layer 4 andthe receptive layer 3 is transferred from a next intermediate transferrecording medium onto the thermally transferred image 9 in the object11. Preferably, the hologram layer 4 in the transfer portion 8B has nohologram image, the receptive layer 3 in the transfer portion 8B has nothermally transferred image, and the transfer portion 8B is transparentso that, when the thermally transferred image 9 and hologram image 10underlying the transfer portion 8B in the print are observed, no troubleoccurs.

FIG. 6 is a cross-sectional view showing one embodiment of the finalprint produced according to the present invention. The print shown inFIG. 6 has the same construction as the print shown in FIG. 4, exceptthat a hologram layer 4 has been provided instead of the intermediatelayer and the hologram image provided in the hologram layer 4 in thetransfer portions 8A is different from the hologram image provided inthe hologram layer 4 in the transfer portions 8B. Therefore, the printshown in FIG. 6 is different from the print shown in FIG. 5.

The print shown in FIG. 6 is produced from an intermediate transferrecording medium with a hologram, wherein a transfer portion 8 providedon a substrate film comprises a hologram layer 4 and a receptive layer 3provided in that order on the substrate film and, in the hologram layer,at least two different hologram images 10A and 10B are alternatelyprovided as counted on the assumption that one image is provided in oneimage plane. An image 9 is thermally transferred onto the intermediatetransfer recording medium in its transfer portion 8A which is thetransfer portion 8 in its portion corresponding to one image plane withthe hologram image 10A formed thereon. Next, the transfer portion 8Awith the image formed thereon is transferred on the object 11, and,thereafter, the transfer portion 8B, comprising the hologram layer 4 andthe receptive layer 3, which is the transfer portion 8 in its portioncorresponding to one image plane with the hologram image 10B formedthereon, is transferred from the intermediate transfer recording mediumonto the thermally transferred image 9 on the object 11. In this case,the hologram images 10A and 10B are provided at respective positionsdifferent from each other in the thicknesswise direction, that is, areprovided in respective different layers, so as to cover the thermallytransferred image 9. Therefore, in the print 12, the forgery andalteration can be fully prevented.

In the method for image formation according to the present invention,specified thermally transferred image and/or hologram image (in somecases, a combination of different hologram images) are stacked andtransferred onto an object at its predetermined positions. In order toaccurately perform registration of each thermal transfer at the time ofthe thermal transfer of the image and at the time of the thermaltransfer of the hologram image, a method is preferably adopted whereinmarks commonly used in the positional detection at the time of eachtransfer are provided and are detected with a detector and the detectoris interlocked with a thermal transfer apparatus to perform registrationfor thermal transfer.

EXAMPLES Example 1

A 12 μm-thick transparent polyethylene terephthalate film was firstprovided as a substrate film. The following coating liquid for a peellayer was coated on the surface of the substrate film, and the coatingwas dried to form a 1.5 μm-thick peel layer on the substrate film.

(Coating liquid for peel layer) Acrylic resin 40 parts Polyester resin 2parts Methyl ethyl ketone 50 parts Toluene 50 parts

An ultraviolet-curable acrylic resin (“Yupimer LZ 065 S,” manufacturedby Mitsubishi Chemical Corporation) was then coated onto the peel layerby gravure reverse coating. The coating was exposed to ultraviolet lightand was dried to form a 2.0 μm-thick hologram layer. A hologram patternwas formed in the hologram layer by providing an original plate having aconcave/convex pattern of interference fringes of a hologram and formingfine concaves and convexes by embossing.

Further, a 500 angstrom-thick titanium oxide layer was vacuum depositedas a transparent vapor deposited layer on the hologram layer with ahologram pattern formed thereon. The following coating liquid for areceptive layer was further coated onto the transparent vapor depositedlayer, and the coating was dried to form a 2.0 μm-thick receptive layer.

(Coating liquid for receptive layer) Vinyl chloride-vinyl acetatecopolymer 40 parts Acryl silicone 1.5 parts Methyl ethyl ketone 50 partsToluene 50 parts

Thus, the peel layer, the hologram layer, the transparent vapordeposited layer, and the receptive layer were provided in that order onthe substrate film. The hologram image provided in the hologram layerwas as shown in FIG. 1. That is, the hologram image was provided in thetransfer portion of the intermediate transfer recording medium everyother image plane.

Thus, an intermediate transfer recording medium of Example 1 wasprepared.

An image was thermally transferred, on a receptive layer (image planeportion 13A) in the intermediate transfer recording medium, using athermal transfer sheet comprising colorant layers of yellow, magenta,and cyan provided in a face serial manner.

Thereafter, a transfer portion 8A with the above image formed thereonwas transferred onto a passport (an object) at its predeterminedposition.

Next, the intermediate transfer recording medium in its transfer portion8B (corresponding to the image plane portion 13B in FIG. 1) wastransferred once again on the thermally transferred image in thepassport with the image formed thereon to produce a print as shown inFIG. 5.

Example 2

A peel layer, a hologram layer, a transparent vapor deposited layer, anda receptive layer were provided in that order on a substrate film in thesame manner as in Example 1, except that the hologram image was formedas shown in FIG. 2, that is, two types of hologram images 10A and 10Bwere alternately and repeatedly provided in the transfer portions in theintermediate transfer recording medium as counted on the assumption thatone image is set in one image plane.

Thus, an intermediate transfer recording medium of Example 2 wasprepared.

An image was thermally transferred, on a receptive layer (image planeportion 13A) in the intermediate transfer recording medium, using athermal transfer sheet comprising colorant layers of yellow, magenta,and cyan provided in a face serial manner.

Thereafter, a transfer portion 8A with the above image formed thereonwas transferred onto a passport (an object) at its predeterminedposition.

Next, the intermediate transfer recording medium in its transfer portion8B (corresponding to the image plane portion 13B in FIG. 2) wastransferred once again on the thermally transferred image in thepassport with the image formed thereon to produce a print as shown inFIG. 6.

Comparative Example 1

A peel layer, a hologram layer, a transparent vapor deposited layer, anda receptive layer were provided in that order on a substrate film in thesame manner as in Example 1, except that the hologram image wascontinuously formed. Thus, an intermediate transfer recording medium ofComparative Example 1 was prepared.

An image was thermally transferred, on a receptive layer in theintermediate transfer recording medium, using a thermal transfer sheetcomprising colorant layers of yellow, magenta, and cyan provided in aface serial manner. Thereafter, a transfer portion with the above imageformed thereon was transferred onto a passport (an object) at itspredetermined position to prepare a print.

Evaluation Results

For the prints prepared in Examples 1 and 2, the transferred portionwith the thermally transferred image formed thereon is provided on theobject, and the transferred portion as the outermost surface in thefinal form of the print is superimposed once on the transferred portionwith the thermally transferred image formed thereon. By virtue of this,a strong film for protecting the thermally transferred image can beprovided, and, even when the prints had been exposed to serviceconditions, which are severe in terms of various fastness propertiessuch as chemical resistance, lightfastness, and weathering resistance,the thermally transferred image was not damaged. Further, the printsprepared in the examples of the present invention have a hologram imagein its transferred portion and thus are excellent in the prevention ofthe forgery and alteration of the thermally transferred image of writtencontents or the like.

On the other hand, when the print prepared in Comparative Example 1 hadbeen exposed to service conditions, which are severe in terms of variousfastness properties such as chemical resistance, lightfastness, andweathering resistance, the thermally transferred image was damaged, and,as a result, a portion of the image became illegible.

As described above, in the method for image formation according to thepresent invention, an intermediate transfer recording medium comprisinga substrate film and a transfer portion provided separably on thesubstrate film is provided, and an image is formed on the intermediatetransfer recording medium in its transfer portion. The transfer portionis transferred onto an object, and, thereafter, the intermediatetransfer recording medium in its next transfer portion is againtransferred once or more onto the object with the image formed thereon.In this case, preferably, in the intermediate transfer recording medium,a hologram image is set every at least second image plane and an imageis formed on the transfer portion having the hologram image.

Further, a method for image formation may also be adopted whichcomprises the steps of: providing an intermediate transfer recordingmedium with a hologram, wherein a transfer portion is provided which hasat least two different hologram images alternately provided in the imageplane portions as counted on the assumption that one image is set in oneimage plane; forming an image on the transfer portion in its regionhaving one type of hologram image; transferring the transfer portiononto an object; and, thereafter, again transferring the intermediatetransfer recording medium, with a hologram, in its next transfer portiononce or more onto the object with the image formed thereon.

Thus, the transferred portion with the thermally transferred imageformed thereon is provided on the object, and the transferred portion asthe outermost surface in the final form of the print is superimposedonce or more on the transferred portion with the thermally transferredimage formed thereon. By virtue of this, a strong film for protectingthe thermally transferred image can be provided, and, even when theprint is exposed to severe service conditions, the thermally transferredimage is excellent in various fastness properties.

Further, the provision of a transferred portion having a thermallytransferred image and a hologram image in the print can impart betterprevention of the forgery and alteration of the thermally transferredimage to the print.

What is claimed is:
 1. A method for image formation, comprising thesteps of: providing an intermediate transfer recording medium comprisinga substrate film and at least a first transfer portion and a secondtransfer portion provided separably on the substrate film, the firsttransfer portion comprising a thermally transferable colorant receptivelayer; forming an image on the first transfer portion of theintermediate transfer recording medium; first transferring the firsttransfer portion having the image onto an object; and, secondtransferring the second transfer portion of the intermediate transferrecording medium onto the first transfer portion formed on the object,thereby forming a laminate structure comprising the first transferportion and the second transfer portion on the object.